Structural and biomechanical properties of fixed bovine pericardium heart valve prostheses are not affected by ionizing radiation: an in-vitro study

Objective: Precocious structural degeneration of bioprostheses in irradiated survivors of chest malignancies has been reported. Aim of this in-vitro study was to evaluate any structural and/or biomechanical radiation-induced changes on a fixed bovine peri-cardium used to manufacture prosthetic heart valve leaflets. Methods: Fixed-pericardial bovine patches underwent irradia-tion with a c-rays source IBL 437C, according to experimental radiobiological protocols (T1: single-2-Gray (Gy) dose in 15+/- sec; T2: single-10-Gy dose in 76+/-7 sec; T3: single-30-Gy dose in 230 sec; T4: fractioned radiation 3-Gy dose in 23 sec /session, 910 sessions; T0: controls). Specimen assessment included mechanical traction test (strain-stress and load to breakage point), shrinkage test (contraction temperature) and histological examination (hematoxylin/eosin for tissue features, Azan for collagen fibers, Verhoeff/VanGieson for elastin fibers). Results: Mechanical traction tests did not show remarkable variations in traction load values. Contrac-tion temperature (°C) did not show any significant difference among the specimen, with only a trend towards a mild increase in the mean shrinkage temperature in all radiated samples vs T0. There were no remarkable histological differences, with irradiated samples maintain-ing the same architecture of elastic fibers and collagen bundles, as well as the same cellular and vascular content of controls. Conclusions: In-vitro, ionizing radiations do not seem to induce any biomechanical and/or structural changes on fixed bovine pericardium. In-vivo studies are required to evaluate the potential role of endogenous factors in inducing radiation mediated prostheses tissue degeneration.